Method of etching silicon oxide and silicon nitride selectively against each other

ABSTRACT

Silicon oxide and silicon nitride can be etched selectively against each other with high efficiency. A method includes preparing a processing target object within a chamber; etching the silicon oxide of the processing target object by generating plasma of a processing gas containing carbon, hydrogen and fluorine within the chamber in a state that a temperature of the processing target object is set to a first temperature; and etching the silicon nitride of the processing target object by generating the plasma of the processing gas containing carbon, hydrogen and fluorine within the chamber in a state that the temperature of the processing target object is set to a second temperature higher than the first temperature.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2016-180582 filed on Sep. 15, 2016, the entire disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

The embodiments described herein pertain generally to an etching method;and, more particularly, to a method of etching silicon oxide and siliconnitride selectively against each other.

BACKGROUND

In the manufacture of an electronic device such as a semiconductordevice, plasma etching may be performed by using a plasma processingapparatus. When performing the plasma etching, plasma of a processinggas is generated within a chamber main body of the plasma processingapparatus. An etching target region of a processing target object isetched by ions and/or radicals in the generated plasma.

An example of the etching target region may be a region made of siliconoxide. In the plasma etching of the silicon oxide, plasma of aprocessing gas containing fluorocarbon and/or hydrofluorocarbon isgenerated. Such plasma etching of the silicon oxide is described inPatent Document 1.

Patent Document 1: Japanese Patent Laid-open Publication No. H07-147273

Meanwhile, a processing target object may have a region made of siliconoxide and a region made of silicon nitride. In the plasma etching ofsuch a processing target object, it may be required to etch the siliconoxide and the silicon nitride selectively against each other. Further,in this etching of the silicon oxide and the silicon nitride, it is alsorequired to etch them efficiently.

SUMMARY

In an exemplary embodiment, there is provided a method of etchingsilicon oxide and silicon nitride selectively against each other. Themethod includes (i) preparing a processing target object within achamber provided by a chamber main body of a plasma processingapparatus; (ii) etching silicon oxide of the processing target object bygenerating plasma of a processing gas containing carbon, hydrogen andfluorine within the chamber in a state that a temperature of theprocessing target object is set to a first temperature; and (iii)etching silicon nitride of the processing target object by generatingthe plasma of the processing gas containing carbon, hydrogen andfluorine within the chamber in a state that the temperature of theprocessing target object is set to a second temperature higher than thefirst temperature.

An etching rate of the silicon oxide becomes higher than an etching rateof the silicon nitride at a relatively low temperature. Meanwhile, theetching rate of the silicon nitride becomes higher than the etching rateof the silicon oxide at a relatively high temperature. In the exemplaryembodiment, the etching is performed by the plasma of the processing gasin the state that the temperature of the processing target object is setto the first temperature which is relatively low. Accordingly, thesilicon oxide is etched selectively with high efficiency against thesilicon nitride. Furthermore, the etching is performed by the plasma ofthe processing gas in the state that the temperature of the processingtarget object is set to the second temperature which is higher than thefirst temperature. Accordingly, the silicon nitride is etchedselectively with high efficiency against the silicon oxide. Therefore,according to the method, it is possible to etch the silicon oxide andthe silicon nitride selectively against each other with high efficiency.

The processing target object may have multiple first layers made of thesilicon oxide and multiple second layers made of the silicon nitride.The multiple first layers and the multiple second layers may bealternately stacked on top of each other. The etching of the siliconoxide and the etching of the silicon nitride may be performedalternately. In this exemplary embodiment, the multilayered film can beefficiently etched.

The first temperature may be lower than −30° C., and the secondtemperature may be higher than −30° C.

The plasma processing apparatus may further include an analyzerconfigured to perform spectroscopic analysis of the plasma within thechamber. The etching of the silicon oxide may be ended when it isdetermined, based on a light emission intensity of CO obtained by theanalyzer, that the silicon oxide is completely etched. Further, theetching of the silicon nitride may be ended when it is determined, basedon a light emission intensity of CN obtained by the analyzer, that thesilicon nitride is completely etched.

The plasma processing apparatus may further include a mounting table, achiller unit, a gas exhaust device and a pipeline system. The mountingtable may be provided within the chamber and include a cooling tablemade of a metal and an electrostatic chuck. A path for a coolant may beprovided within the cooling table. The electrostatic chuck may beprovided on the cooling table with a heat transfer space therebetweenand provided with a heater therein. The chiller unit may be configuredto supply the coolant into the path of the cooling table. The pipelinesystem may be configured to connect the chiller unit and the gas exhaustdevice to the heat transfer space selectively. The method may furtherinclude decreasing the temperature of the processing target object bysupplying the coolant into the path and the heat transfer space from thechiller unit; and increasing the temperature of the processing targetobject by decompressing the heat transfer space with the gas exhaustdevice and generating heat from the heater. The etching of the siliconoxide may be performed after the temperature of the processing targetobject is set to the first temperature by performing the decreasing ofthe temperature of the processing target object. Further, the etching ofthe silicon nitride may be performed after the temperature of theprocessing target object is set to the second temperature by performingthe increasing of the temperature of the processing target object. Ifthe coolant is supplied into the heat transfer space, the heatresistance between the electrostatic chuck and the cooling table isreduced, so that the temperature of the electrostatic chuck can bereduced at a high speed. Accordingly, before the etching of the siliconoxide is performed, the temperature of the processing target object canbe reduced at a high speed. Further, if the heat transfer space isdecompressed, the heat resistance between the electrostatic chuck andthe cooling table is increased, so that the temperature of theelectrostatic chuck can be increased at a high speed. Accordingly,before the etching of the silicon nitride is performed, the temperatureof the processing target object can be increased at a high speed. Thus,according to the exemplary embodiment, the silicon oxide and the siliconnitride can be etched selectively against each other with highefficiency.

According to the exemplary embodiments as described above, it ispossible to etch the silicon oxide and the silicon nitride selectivelyagainst each other with high efficiency.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description that follows, embodiments are described asillustrations only since various changes and modifications will becomeapparent to those skilled in the art from the following detaileddescription. The use of the same reference numbers in different figuresindicates similar or identical items.

FIG. 1 is a flowchart for describing a method of etching silicon oxideand silicon nitride selectively against each other according to anexemplary embodiment;

FIG. 2 is an enlarged sectional view illustrating a part of an exampleprocessing target object;

FIG. 3 is a diagram schematically illustrating a plasma processingapparatus according to the exemplary embodiment that can be used toperform the method shown FIG. 1;

FIG. 4 is an enlarged sectional view illustrating a part of theprocessing target object at a time when the method MT is beingperformed;

FIG. 5 is an enlarged sectional view illustrating a part of theprocessing target at a time when the method MT is being performed;

FIG. 6 is an enlarged sectional view illustrating a part of theprocessing target object at a time when the method MT is completed;

FIG. 7 is a graph showing temperature dependency of an etching rate ofthe silicon oxide and an etching rate of the silicon nitride;

FIG. 8 is an enlarged sectional view illustrating a part of anotherexample processing target object;

FIG. 9 is a diagram schematically illustrating a plasma processingapparatus according to another exemplary embodiment that can be used inperforming the method shown in FIG. 1;

FIG. 10 is an enlarged sectional view illustrating a part of a mountingtable of the plasma processing apparatus shown in FIG. 9;

FIG. 11 is an enlarged sectional view illustrating another part of themounting table of the plasma processing apparatus shown in FIG. 9;

FIG. 12 is a diagram illustrating a pipeline system according to theexemplary embodiment;

FIG. 13 is a diagram illustrating a state of the pipeline system of theplasma processing apparatus shown in FIG. 9 in an example process ST2;and

FIG. 14 is a diagram illustrating a state of the pipeline system of theplasma processing apparatus shown in FIG. 9 in an example process ST7.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part of the description. In thedrawings, similar symbols typically identify similar components, unlesscontext dictates otherwise. Furthermore, unless otherwise noted, thedescription of each successive drawing may reference features from oneor more of the previous drawings to provide clearer context and a moresubstantive explanation of the current exemplary embodiment. Still, theexemplary embodiments described in the detailed description, drawings,and claims are not meant to be limiting. Other embodiments may beutilized, and other changes may be made, without departing from thespirit or scope of the subject matter presented herein. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein and illustrated in the drawings, may bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

Hereinafter, various exemplary embodiments will be described in detailwith reference to the accompanying drawings. Same or corresponding partsin the various drawings will be assigned same reference numerals.

FIG. 1 is a flowchart for describing a method according to an exemplaryembodiment. A method MT shown in FIG. 1 is directed to etching siliconoxide and silicon nitride of a processing target object selectivelyagainst each other. In the method shown in FIG. 1, a process ST1 isfirst performed. In the process ST1, a processing target object isprepared in a chamber of a plasma processing apparatus.

FIG. 2 is an enlarged sectional view illustrating a part of an exampleprocessing target object. An example processing target object W1 shownin FIG. 2 has a plurality of first layers L1 and a multiplicity ofsecond layers L2. The first layers L1 are made of silicon oxide. Thesecond layers L2 are made of silicon nitride. The first layers L1 andthe second layers L2 are alternately stacked on top of each other on asubstrate SB. That is, the processing target object W1 has amultilayered film composed of the layers made of silicon oxide and thelayers made of silicon nitride. A mask MK is provided on top of theuppermost layer of the multilayered film. The processing target objectW1 may have, for example, a disk shape. The mask MK of the processingtarget object W1 is provided with multiple openings distributed in asurface thereof. The openings of the mask MK are, by way of example,holes or grooves. Further, the processing target object to which themethod MT is applied may not necessarily have the multilayered film aslong as the processing target object has one or more first regions madeof silicon oxide and one or more second regions made of silicon nitride.Further, the one or more first regions and the one or more secondregions may not be stacked on top of each other.

FIG. 3 is a diagram illustrating a plasma processing apparatus accordingto the exemplary embodiment that can be used in performing the methodshown in FIG. 1. A plasma processing apparatus 10 shown in FIG. 3 isconfigured as a capacitively coupled plasma processing apparatus. Theplasma processing apparatus 10 includes a chamber main body 12. Thechamber main body 12 has a substantially cylindrical shape, and aninternal space of the chamber main body 12 is configured as a chamber 12c. The chamber main body 12 is made of a metal such as, but not limitedto, aluminum. A film having plasma resistance, for example, an alumitefilm or an yttrium oxide film is formed on an inner wall surface of thechamber main body 12. The chamber main body 12 is grounded.

Within the chamber 12 c, a supporting member 14 is provided on a bottomportion of the chamber main body 12. The supporting member 14 is made ofan insulating material. The supporting member 14 has a substantiallycylindrical shape. Within the chamber 12 c, the supporting member 14 isupwardly extended from the bottom portion of the chamber main body 12.The supporting member 14 is configured to support a mounting table 16 onan upper portion thereof.

The mounting table 16 includes a lower electrode 18 and an electrostaticchuck 20. The lower electrode 18 includes a first member 18 a and asecond member 18 b. The first member 18 a and the second member 18 b aremade of a conductor such as, but not limited to, aluminum, and each hasa substantially disk shape. The second member 18 b is provided on thefirst member 18 a and electrically connected with the first member 18 a.The electrostatic chuck 20 is provided on the lower electrode 18.

The electrostatic chuck 20 is configured to hold a processing targetobject W placed thereon. The electrostatic chuck 20 has a disk-shapedinsulating layer and a film-shaped electrode embedded in the insulatinglayer. The electrode of the electrostatic chuck 20 is electricallyconnected to a DC power supply 22. The electrostatic chuck 20 attractsand holds the processing target object W by an electrostatic forcegenerated by a DC voltage applied from the DC power supply 22. A heatermay be provided within this electrostatic chuck 20.

A focus ring FR is provided on a peripheral portion of the lowerelectrode 18 to surround an edge of the processing target object W andthe electrostatic chuck 20. The focus ring FR is provided to improveuniformity of etching. The focus ring FR is made of a material which isappropriately selected depending on a material of the etching target. Byway of non-limiting example, the focus ring FR may be made of quartz.

A path 18 f for a coolant is formed in the second member 18 b of thelower electrode 18. A coolant is supplied into the path 18 f from achiller unit 24 provided outside the chamber main body 12 via a pipeline24 a. The coolant supplied into the path 18 f is returned back into thechiller unit 24 through a pipeline 24 b. The chiller unit 24 isconfigured to control a temperature of the coolant supplied into thepath 18 f. As the temperature of the coolant supplied into the path 18 fis controlled, a temperature of the processing target object W placed onthe electrostatic chuck 20 is controlled.

The plasma processing apparatus 10 is equipped with a gas supply line28. Through the gas supply line 28, a heat transfer gas, for example, aHe gas, is supplied from a heat transfer gas supply device into a gapbetween a top surface of the electrostatic chuck 20 and a rear surfaceof the processing target object W.

The plasma processing apparatus 10 is further equipped with an upperelectrode 30. The upper electrode 30 is placed above the mounting table16, facing the mounting table 16. The upper electrode 30 is supported atan upper portion of the chamber main body 12 with an insulating member32 therebetween. The upper electrode 30 may include a ceiling plate 34and a supporting body 36. The ceiling plate 34 is directly contact withthe chamber 12 c, and is provided with a multiple number of gasdischarge holes 34 a. This ceiling plate 34 may be made of a conductoror a semiconductor having low resistance with low Joule heat.

The supporting body 36 is configured to support the ceiling plate 34 ina detachable manner, and is made of a conductor such as, but not limitedto, aluminum. A gas diffusion space 36 a is formed within the supportingbody 36. Multiple holes 36 b are extended downwards from the gasdiffusion space 36 a to communicate with the gas discharge holes 34 a,respectively. Further, the supporting body 36 is provided with a port 36c through which a processing gas is introduced into the gas diffusionspace 36 a, and a pipeline 38 is connected to this port 36 c.

The pipeline 38 is connected to a gas source group 40 via a valve group42 and a flow rate controller group 44. The gas source group 40 includesa plurality of gas sources for supplying a processing gas containingcarbon, hydrogen and fluorine into the chamber 12 c. The plurality ofgas sources at least includes a gas source of a hydrogen-containing gasand a gas source of a fluorine-containing gas. Here, thehydrogen-containing gas may be, by way of non-limiting example, ahydrogen gas (H₂ gas), a hydrocarbon gas or a hydrofluorocarbon gas. Thefluorine-containing gas may be, by way of example, but not limitation, afluorocarbon gas, a hydrofluorocarbon gas, a nitrogen trifluoride gas(NF₃ gas) or a sulfur hexafluoride gas (SF₆ gas). As an example, theplurality of gas sources may include a gas source of a H₂ gas, a gassource of a CF₄ gas, a gas source of a CHF₃ gas and a gas source of aNF₃ gas. As another example, the plurality of gas sources may include agas source of a H₂ gas, a gas source of a CF₄ gas, a gas source of aCH₂F₂ gas and a gas source of a NF₃ gas.

The valve group 42 includes a plurality of valves, and the flow ratecontroller group 44 includes a plurality of flow rate controllers. Eachof the flow rate controllers may be implemented by a mass flowcontroller or a pressure control type flow rate controller. Each of thegas sources belonging to the gas source group 40 is connected to thepipeline 38 via the corresponding flow rate controller belonging to theflow rate controller group 44 and the corresponding valve belonging tothe valve group 42.

Further, in the plasma processing apparatus 10, a shield member 46 isprovided along an inner wall of the chamber main body 12 in a detachablemanner. The shield member 46 is also provided on an outer side surfaceof the supporting member 14. The shield member 46 is configured tosuppress an etching byproduct from adhering to the chamber main body 12.The shield member 46 may be prepared by coating an aluminum member withceramics such as Y₂O₃.

A baffle plate 48 is provided between the supporting member 14 and theinner wall of the chamber main body 12. The baffle plate 48 is providedwith a plurality of holes which are formed through the baffle plate 48in a thickness direction thereof. The baffle plate 48 may be made of, byway of example, an aluminum member coated with ceramics such as Y₂O₃.The chamber main body 12 is also provided with a gas exhaust opening 12e under the baffle plate 48. The gas exhaust opening 12 e is connectedwith a gas exhaust device 50 via a gas exhaust line 52. The gas exhaustdevice 50 includes a vacuum pump such as a turbo molecular pump, and iscapable of decompressing the chamber 12 c. Further, an opening 12 p forcarry-in and carry-out of the processing target object W is provided ata side wall of the chamber main body 12, and the opening 12 p isopened/closed by a gate valve GV.

The plasma processing apparatus 10 further includes a first highfrequency power supply 62 and a second high frequency power supply 64.The first high frequency power supply 62 is configured to generate afirst high frequency power for plasma generation. A frequency of thefirst high frequency power is in the range from 27 MHz to 100 MHz, forexample, 40 MHz. The first high frequency power supply 62 is connectedto the lower electrode 18 via a matching device 66. The matching device66 is equipped with a circuit configured to match an output impedance ofthe first high frequency power supply 62 and an input impedance at aload side (lower electrode 18 side). The first high frequency powersupply 62 may be connected to the upper electrode 30 via the matchingdevice 66.

The second high frequency power supply 64 is configured to generate asecond high frequency power for ion attraction into the processingtarget object W. A frequency of the second high frequency power rangesfrom 400 kHz to 13.56 MHz, for example, 3 MHz. The second high frequencypower supply 64 is connected to the lower electrode 18 via a matchingdevice 68. The matching device 68 is equipped with a circuit configuredto match an output impedance of the second high frequency power supply64 and the input impedance at the load side (lower electrode 18 side).

Further, the plasma processing apparatus 10 may further include a DCpower supply 70. The DC power supply 70 is connected to the upperelectrode 30. The DC power supply 70 is configured to generate anegative DC voltage to apply this negative DC voltage to the upperelectrode 30.

The plasma processing apparatus 10 may be further equipped with ananalyzer 72. The analyzer 72 is configured to perform spectroscopicanalysis of plasma generated within the chamber 12 c. By way of example,the analyzer 72 observes emission of plasma through a window 74 providedat the side wall of the chamber main body 12. The window 74 is made of atransparent material such as quartz. The analyzer 72 detects at least alight emission intensity of CO and a light emission intensity of CN. Theemitted light of CO has a wavelength of about 483 nm, and the emittedlight of CN has a wavelength of about 387 nm.

The plasma processing apparatus 10 may further include a control unitCU. The control unit CU is implemented by a computer including aprocessor, a storage unit, an input device, a display device, and soforth, and is configured to control individual components of the plasmaprocessing apparatus 10. In the control unit CU, an operator can inputcommands through the input device to manage the plasma processingapparatus 10. Further, an operational status of the plasma processingapparatus 10 can be visually displayed on the display device. Further,the storage unit of the control unit CU stores therein recipe data andcontrol programs for controlling various processings performed in theplasma processing apparatus 10 by the processor. For example, thestorage unit of the control unit CU stores therein control programs forimplementing the method MT in the plasma processing apparatus 10 andrecipe data.

Now, the method MT will be explained for an example case where themethod MT is applied to the processing target object W1 by using theplasma processing apparatus 10. Here, however, it should be noted that aplasma processing apparatus used to perform the method MT is not limitedto the plasma processing apparatus 10 and a processing target object towhich the method MT is applied is not limited to the processing targetobject W1.

Reference is made to FIG. 1 again and FIG. 4 to FIG. 6 as well. FIG. 4and FIG. 5 are enlarged sectional views illustrating a part of theprocessing target object at a time when the method MT is beingperformed. FIG. 6 is an enlarged sectional view illustrating a part ofthe processing target object at a time when the method MT is completed.

As stated above, in the process ST1 of the method MT, the processingtarget object W1 as shown in FIG. 2 is prepared within the chamber 12 c.The processing target object W1 is placed on and held by theelectrostatic chuck 20.

Then, a process ST2 is performed. In the process ST2, a temperature ofthe processing target object W1 is reduced. To elaborate, in response toa signal from the control unit CU, the chiller unit 24 adjusts thetemperature of the coolant supplied to the path 18 f. Accordingly, thetemperature of the processing target object W1 is reduced to reach afirst temperature. The first temperature is, for example, lower than−30° C.

Subsequently, a process ST3 is performed. In the process ST3, while thetemperature of the processing target object W1 is set to the firsttemperature, the silicon oxide of the processing target object W1 isetched. In the process ST3, in response to a signal from the controlunit CU, individual components of the plasma processing apparatus 10 iscontrolled. Accordingly, the processing gas containing carbon, hydrogenand fluorine is supplied into the chamber 12 c. As an example, theprocessing gas may contain a H₂ gas, a CF₄ gas, a CHF₃ gas and a NF₃gas. As another example, the processing gas may contain a H₂ gas, a CF₄gas, a CH₂F₂ gas and a NF₃ gas. Further, in the process ST3, the chamber12 c is decompressed. Further, the temperature-adjusted coolant issupplied into the path 18 f from the chiller unit 24 to maintain theprocessing target object W1 at the first temperature. Furthermore, thefirst high frequency power is supplied to the lower electrode 18 fromthe first high frequency power supply 62, and the second high frequencypower may be supplied to the lower electrode 18 from the second highfrequency power supply 64. By performing the process ST3, plasma of theprocessing gas is generated within the chamber 12 c. The silicon oxideis etched by active species such as ions and/or radicals in this plasma.To elaborate, a portion of the first layer L1 exposed through an openingof the mask MK is etched.

Thereafter, a process ST4 is performed, and a process ST5 is thenperformed. The process ST4 and the process ST5 are conducted until theetching of the silicon oxide of the process ST3 is ended. In the processST4, the light emission intensity of CO is detected by the analyzer 72.The detected light emission intensity is sent to the control unit CU.

In the process ST5, it is determined by the control unit CU whether acondition for stopping the process ST3 is satisfied. To be specific, inthe process ST5, based on the light emission intensity of the COdetected in the process ST4, it is determined by the control unit CUwhether the etching of the silicon oxide has been completed. During theprocess ST3, the CO is generated as the oxygen generated by the etchingof the silicon oxide is bond with the carbon contained in the processinggas. The light emission intensity of the CO thus generated is reducedwhen the etching of the silicon oxide is ended. Thus, based on timesseries values of the light emission intensity of the CO, it can bedetermined whether the etching of the silicon oxide has been finished.For example, if the light emission intensity of the CO is decreased at apreset rate during the process ST3 or if an absolute value of a timederivative of the light emission intensity of the CO is increased over apreset value during the process ST3, it can be determined that theetching of the silicon oxide has been ended. Further, the process ST3may be ended after a lapse of a predetermined time from the beginningthereof.

If it is determined in the process ST5 that the etching of the siliconoxide is not finished yet, the processing from the process ST4 iscontinued again while performing the process ST3. Meanwhile, if it isdetermined in the process ST5 that the etching of the silicon oxide hasbeen ended, the process ST3 is ended. If a first cycle of the processST3 is ended as the uppermost first layer L1 is etched, a second layerL2 under the uppermost first layer L1 is exposed through the opening ofthe mask MK, as illustrated in FIG. 4. Further, an etching rate of thesilicon nitride is much lower than an etching rate of the silicon oxideat the temperature (first temperature) of the processing target objectW1 during the process ST3. Accordingly, even when the etching of thefirst layer L1 is finished, the second layer L2 under the first layer L1is hardly etched as compared to the first layer L1.

Subsequently, the process ST6 is conducted. In the process ST6, it isdetermined by the control unit CU whether the etching of a preset numberof layers of the processing target object W1 has been ended. Here, the“preset number” may be the total number of all layers of the processingtarget object, or may be a number smaller than the total number of thelayers. If it is determined in the process ST6 that the present numberof layers are all etched, the method MT is ended. Meanwhile, if it isdetermined that the etching of the preset number of layers is notcompleted yet, the processing proceeds to a process ST7.

In the process ST7, the temperature of the processing target object W1is increased. To elaborate, in response to a signal from the controlunit CU, the chiller unit 24 adjusts the temperature of the coolantsupplied to the path 18 f. Further, in the process ST7, the heaterembedded in the electrostatic chuck 20 may generate heat. As a result,the temperature of the processing target object W1 is raised to reach asecond temperature. The second temperature is higher than the firsttemperature. By way of example, the second temperature may be higherthan −30° C.

Then, a process ST8 is conducted. In the process ST8, etching of thesilicon nitride of the processing target object W1 is performed in thestate that the temperature of the processing target object W1 is set tothe second temperature. In the process ST8, in response to a signal fromthe control unit CU, the individual components of the plasma processingapparatus 10 are controlled. Accordingly, the processing gas containingcarbon, hydrogen and fluorine is supplied into the chamber 12 c. As anexample, the processing gas may contain a H₂ gas, a CF₄ gas, a CHF₃ gasand a NF₃ gas. As another example, the processing gas may contain a H₂gas, a CF₄ gas, a CH₂F₂ gas and a NF₃ gas. Further, in the process ST8,the chamber 12 c is decompressed. Further, a temperature-adjustedcoolant is supplied into the path 18 f from the chiller unit 24 tomaintain the processing target object W1 at the second temperature.Heating by the heater embedded in the electrostatic chuck 20 may also beperformed. Furthermore, the first high frequency power is supplied tothe lower electrode 18 from the first high frequency power supply 62,and the second high frequency power may be supplied to the lowerelectrode 18 from the second high frequency power supply 64. Byperforming the process ST8, plasma of the processing gas is generatedwithin the chamber 12 c. The silicon nitride is etched by active speciessuch as ions and/or radicals in this plasma. To elaborate, a portion ofthe second layer L2 exposed through the opening of the mask MK isetched.

Thereafter, a process ST9 is performed, and a process ST10 is thenperformed. The process ST9 and the process ST10 are conducted until theetching of the silicon nitride of the process ST8 is ended. In theprocess ST9, a light emission intensity of CN is detected by theanalyzer 72. The detected light emission intensity is sent to thecontrol unit CU.

In the process ST10, it is determined by the control unit CU whether acondition for stopping the process ST8 is satisfied. To be specific, inthe process ST10, based on the light emission intensity of the CNdetected in the process ST9, it is determined by the control unit CUwhether the etching of the silicon nitride has been ended. During theprocess ST8, the CN is generated as the nitrogen generated by theetching of the silicon nitride is bond with the carbon in the processinggas. The light emission intensity of the CN thus generated is reducedwhen the etching of the silicon nitride is ended. Thus, based on timesseries values of the light emission intensity of the CN, it can bedetermined whether the etching of the silicon nitride has been finished.For example, if the light emission intensity of the CN is decreased at apreset rate during the process ST8 or if an absolute value of a timederivative of the light emission intensity of the CN is increased over apreset value during the process ST8, it can be determined that theetching of the silicon nitride has been ended. Further, the process ST8may be ended after a lapse of a predetermined time from the beginningthereof.

If it is determined in the process ST10 that the etching of the siliconnitride is not finished yet, the processing from the process ST9 iscontinued again while performing the process ST8. Meanwhile, if it isdetermined in the process ST10 that the etching of the silicon nitridehas been ended, the process ST8 is ended. If a first cycle of theprocess ST8 is ended as the second layer L2 is etched, a first layer L1under the second layer L2 is exposed through the opening of the mask MK,as shown in FIG. 5. Further, the etching rate of the silicon oxide ismuch lower than the etching rate of the silicon nitride at thetemperature (second temperature) of the processing target object W1during the process ST8. Accordingly, even when the etching of the secondlayer L2 is ended, the first layer L1 under the second layer L2 ishardly etched.

Thereafter, a process ST11 is performed. The same as in the process ST6,in the process ST11, it is determined by the control unit CU whether theetching of the preset number of layers of the processing target objectW1 has been completed. If it is determined in the process ST11 that thepresent number of layers are not all etched yet, the processing from theprocess ST2 is repeated. Meanwhile, if it is determined in the processST11 that the etching of all the preset number of layers of theprocessing target object W1 is completed, the method MT is ended. As aresult, the pattern of the mask MK is transcribed to the preset numberof layers of the processing target object W1. By way of example, asillustrated in FIG. 6, the pattern of the mask MK is transcribed to allof the first layers L1 and all of the second layers L2.

Now, reference is made to FIG. 7 which presents a graph showing thetemperature dependency of the etching rate of silicon oxide and theetching rate of silicon nitride. In FIG. 7, a horizontal axis representsthe temperature of the processing target object, whereas a vertical axisrepresents the etching rate. The etching rate of the silicon oxide shownin FIG. 7 is obtained by etching the silicon oxide film of theprocessing target object in the plasma processing apparatus 10 whilesetting different temperatures for the processing target object.Further, the etching rate of the silicon nitride shown in FIG. 7 isacquired by etching the silicon nitride film of the processing targetobject in the plasma processing apparatus 10 while setting differenttemperatures for the processing target object. Further, variousconditions for etching the silicon oxide film and the silicon nitridefilm are specified as follows.

<Conditions>

Pressure of chamber 12 c: 25 mTorr (3,333 Pa)

First high frequency power: 100 MHz, 2.3 kW

Second high frequency power: 3 MHz, 1 kW

Processing gas: mixed gas of H₂ gas, CF₄ gas, CH₂F₂ gas and NF₃ gas

As can be seen from FIG. 7, in case that the temperature of theprocessing target object is set to be lower than −30° C., the etchingrate of the silicon oxide is higher than the etching rate of the siliconnitride. Particularly, if the temperature of the processing targetobject is set to be equal to or lower than −60° C., the etching rate ofthe silicon oxide is found to be twice as high as the etching rate ofthe silicon nitride. Further, in case that the temperature of theprocessing target object is set to be higher than −30° C., the etchingrate of the silicon nitride is higher than the etching rate of thesilicon oxide. Particularly, if the temperature of the processing targetobject is set to be equal to or higher than 25° C., the etching rate ofthe silicon nitride is found to be twice as high as the etching rate ofthe silicon oxide.

As stated above, the etching rate of the silicon oxide becomes higherthan the etching rate of the silicon nitride at a relatively lowtemperature. Meanwhile, the etching rate of the silicon nitride becomeshigher than the etching rate of the silicon oxide at a relatively hightemperature. In the method MT, the etching is performed by the plasma ofthe processing gas in the state that the temperature of the processingtarget object is set to the first temperature which is relatively low.Accordingly, the silicon oxide is etched selectively with highefficiency against the silicon nitride. Furthermore, in the method MT,the etching is performed by the plasma of the processing gas in thestate that the temperature of the processing target object is set to thesecond temperature which is higher than the first temperature.Accordingly, the silicon nitride is etched selectively with highefficiency against the silicon oxide. Therefore, according to the methodMT, it is possible to etch the silicon oxide and the silicon nitrideselectively against each other with high efficiency.

Further, in case that the processing target object has a multilayeredfilm, like the processing target object W1 shown in FIG. 2, it ispossible to etch the multilayered film efficiently by performing themethod MT. Furthermore, according to the method MT, since the siliconoxide and the silicon nitride can be etched selectively against eachother, if the mask provides a multiple number of openings in anin-surface direction of the processing target object, until the etchingof a same layer under all the openings of the mask is completed, anunderlayer of the corresponding same layer can be suppressed from beingetched. That is, according to the method MT, the uniformity of theetching within the surface of the processing target object can beimproved.

Now, reference is made to FIG. 8, which provides an enlarged sectionalview of a part of another example processing target object. Like theprocessing target object W1, a processing target object W2 shown in FIG.8 includes a plurality of first layers L1 made of silicon oxide and amultiplicity of second layers L2 made of silicon nitride. The firstlayers L1 and the second layers L2 are alternately stacked on top ofeach other. That is, the processing target object W2 has a multilayeredfilm composed of the layers made of silicon oxide and the layers made ofsilicon nitride. In the processing target object W2, however, anuppermost layer of the multilayered film is the second layer L2. In theetching of this processing target object W2, the method MT is modifiedsuch that the processes ST7 to ST11 are first performed before theprocesses ST1 to ST6. That is, the order of performing the processes ST1to ST6 and the processes ST7 to ST11 of the method MT can beappropriately changed based on the structure of the layers of theprocessing target object.

Now, a plasma processing apparatus according to another exemplaryembodiment that can be used in performing the method MT will beexplained. FIG. 9 is a diagram schematically illustrating the plasmaprocessing apparatus according to another exemplary embodiment that canbe used in performing the method shown in FIG. 1. A plasma processingapparatus 100 shown in FIG. 9 is configured as a capacitively coupledplasma processing apparatus. The plasma processing apparatus 100includes a chamber main body 112 and a mounting table 116. The chambermain body 112 has a substantially cylindrical shape, and an internalspace of the chamber main body 112 is configured as a chamber 112 c. Thechamber main body 112 is made of, by way of example, aluminum. A filmmade of ceramic such as an alumite film and/or an yttrium oxide film,which has plasma resistance, is formed on an inner surface of thechamber main body 112. The chamber main body 112 is grounded. Further,an opening 112 p through which a processing target object W is carriedinto/out of the chamber 112 c is provided at a side wall of the chambermain body 112. This opening 112 p is configured to be opened/closed by agate valve GV.

The mounting table 116 is configured to support the processing targetobject W within the chamber 112 c. The mounting table 116 has a functionof attracting the processing target object W and adjusting a temperatureof the processing target object W, and has a structure in which a highfrequency power is sent to a base of an electrostatic chuck. Details ofthis mounting table 116 will be discussed later.

The plasma processing apparatus 100 is further equipped with an upperelectrode 130. The upper electrode 130 is placed within a top opening ofthe chamber main body 112 and is arranged to be substantially parallelto a lower electrode of the mounting table 116. An insulating supportingmember 132 is provided between the upper electrode 130 and the chambermain body 112.

The upper electrode 130 includes a ceiling plate 134 and a supportingbody 136. The ceiling plate 134 has a substantially disk shape. Theceiling plate 134 may have conductivity. Further, the ceiling plate 134is made of, by way of non-limiting example, silicon. Alternatively, theceiling plate 134 is made of aluminum, and a ceramic film having plasmaresistance is formed on a surface of the ceiling plate 134. The ceilingplate 134 is provided with a multiple number of gas discharge holes 134a. These gas discharge holes 134 a are extended in a substantiallyvertical direction.

The supporting body 136 is configured to support the ceiling plate 134in a detachable manner, and is made of, by way of non-limiting example,aluminum. A gas diffusion space 136 a is formed within the supportingbody 136. Multiple holes 136 b are extended from the gas diffusion space136 a to communicate with the gas discharge holes 134 a, respectively. Apipeline 138 is connected to the gas diffusion space 136 a via a port136 c. A gas source group 40 is connected to this pipeline 138 via avalve group 42 and a flow rate controller group 44 in the same way as inthe plasma processing apparatus 10.

The plasma processing apparatus 100 is further equipped with a gasexhaust device 150. The gas exhaust device 150 includes one or more pumpsuch as a turbo molecular pump or a dry pump and a pressure controlvalve. This gas exhaust device 150 is connected to a gas exhaust portformed at the chamber main body 112.

Like the plasma processing apparatus 10, the plasma processing apparatus100 may be further equipped with an analyzer 72. The analyzer 72 isconfigured to perform spectroscopic analysis of plasma generated withinthe chamber 112 c. By way of example, the analyzer 72 observes emissionof plasma through a window 74 provided at the side wall of the chambermain body 112. The window 74 is made of a transparent member such asquartz. The analyzer 72 detects at least a light emission intensity ofCO and a light emission intensity of CN. The emitted light of CO has awavelength of about 483 nm, and the emitted light of CN has a wavelengthof about 387 nm.

The plasma processing apparatus 100 further includes a control unit MCU.The control unit MCU has the same configuration as the control unit CUof the plasma processing apparatus 10. Recipe data and a control programfor controlling various processings performed in the plasma processingapparatus 100 by the processor are stored in a storage unit of thecontrol unit MCU. By way of example, recipe data and control programsfor implementing the method MT in the plasma processing apparatus 100are stored in the storage unit of the control unit MCU.

Now, with reference to FIG. 10 and FIG. 11 in addition to FIG. 9, themounting table 116 and constituent components of the plasma processingapparatus 100 belonging to the mounting table 116 will be discussed indetail. FIG. 10 is an enlarged sectional view illustrating a part of themounting table of the plasma processing apparatus shown in FIG. 9, andFIG. 11 is an enlarged sectional view illustrating another part of themounting table of the plasma processing apparatus illustrated in FIG. 9.

The mounting table 116 includes a cooling table 117 and an electrostaticchuck 120. The cooling table 117 is supported by a supporting member 114upwardly extended from a bottom portion of the chamber main body 112.This supporting member 114 is implemented by an insulating member and ismade of, by way of non-limiting example, aluminum oxide (alumina).Further, the supporting member 114 has a substantially cylindricalshape.

The cooling table 117 is made of a conductive metal, for example,aluminum. The cooling table 117 has a substantially disk shape. Thecooling table 117 has a central portion 117 a and a peripheral portion117 b. The central portion 117 a has a substantially disk shape. Thecentral portion 117 a provides a first top surface 117 c of the coolingtable 117. The first top surface 117 c is of a substantially circularshape.

The peripheral portion 117 b is continuous with the central portion 117a, and is extended in a circumferential direction (a circumferentialdirection with respect to a vertically extended axis line Z) at anoutside of the central portion 117 a in a diametric direction (a radialdirection with respect to the axis line Z). In the present exemplaryembedment, the peripheral portion 117 b provides a bottom surface 117 dof the cooling table 117 along with the central portion 117 a. Further,the peripheral portion 117 b provides a second top surface 117 e. Thesecond top surface 117 e is a band-shaped surface, and is locatedoutside the first top surface 117 c in the diametric direction andextended in the circumferential direction. Further, in the verticaldirection, the second top surface 117 e is located closer to the bottomsurface 117 d than the first top surface 117 c is.

The cooling table 117 is connected with a power feed body 119. The powerfeed body 119 is, by way of example, a power feed rod and is connectedto the bottom surface 117 d of the cooling table 117. The power feedbody 119 is made of aluminum or an aluminum alloy. The power feed body119 is connected to a first high frequency power supply 62 via amatching device 66. Further, the power feed body 119 is electricallyconnected with a second high frequency power supply 64 via a matchingdevice 68.

The cooling table 117 is provided with a path 117 f for a coolant. Thepath 117 f is extended in, for example, a spiral shape within thecooling table 117. The coolant is supplied into the path 117 f from achiller unit TU. In this exemplary embodiment, the coolant supplied intothe path 117 f may be of a type in which heat is absorbed byvaporization thereof to perform cooling. This coolant may be, forexample, a hydrofluorocarbon-based coolant.

The electrostatic chuck 120 is provided on the cooling table 117. Toelaborate, the electrostatic chuck 120 is provided on the first topsurface 117 c of the cooling table 117. The electrostatic chuck 120 hasa base 121 and an attracting member 123. The base 121 constitutes alower electrode and is provided on the cooling table 117. The base 121has conductivity. By way of example, the base 121 may be made of ceramicsuch as aluminum nitride or silicon carbide having conductivity, or madeof a metal (e.g., titanium).

The base 121 has a substantially disk shape. The base 121 has a centralportion 121 a and a peripheral portion 121 b. The central portion 121 ahas a substantially disk shape. The central portion 121 a provides afirst top surface 121 c of the base 121. The first top surface 121 c isof a substantially circular shape.

The peripheral portion 121 b is continuous with the central portion 121a and is extended in a circumferential direction at an outside of thecentral portion 121 a in a diametric direction. In the present exemplaryembedment, the peripheral portion 121 b provides a bottom surface 121 dof the base 121 along with the central portion 121 a. Further, theperipheral portion 121 b provides a second top surface 121 e. The secondtop surface 121 e is a band-shaped surface and extended in thecircumferential direction at an outside of the first top surface 121 cin the diametric direction. Further, in the vertical direction, thesecond top surface 121 e is located closer to the bottom surface 121 dthan the first top surface 121 c is.

The attracting member 123 is provided on the base 121. The attractingmember 123 is coupled to the base 121 by metal bonding with a metalprovided between the attracting member 123 and the base 121. Theattracting member 123 has a substantially disk shape and is made ofceramic. The ceramic forming the attracting member 123 may be one havinga volume resistivity of 1×10¹⁵ Ω·cm or more in a temperature range froma room temperature (e.g., 20° C.) to 400° C. As an example of thisceramic, aluminum oxide (alumina) may be used.

The electrostatic chuck 120 includes a plurality of concentric regionsRN with respect to the axis line Z, that is, a central axis line of theelectrostatic chuck 120. In the exemplary embodiment, the electrostaticchuck 120 includes a first region R1, a second region R2 and a thirdregion R3. The first region R1 intersects with the axis line Z, and thethird region R3 is a region including an edge of the electrostatic chuck120. The second region R2 is located between the first region R1 and thethird region R3. As an example, the first region R1 ranges up to aradius of 120 mm from a center of the electrostatic chuck 120; thesecond region R2 ranges from the radius of 120 mm to a radius of 135 mmof the electrostatic chuck 120; and the third region R3 ranges from theradius of 135 mm to a radius of 150 mm of the electrostatic chuck 120.Further, the number of the regions of the electrostatic chuck 120 may beequal to or larger than 1.

The attracting member 123 of the electrostatic chuck 120 has anattraction electrode 125 embedded therein. The attraction electrode 125is a film-shaped electrode and electrically connected with a DC powersupply 22. If a DC voltage is applied to the attraction electrode 125from the DC power supply 22, the attracting member 123 generates anelectrostatic force such as a Coulomb force to hold the processingtarget object W with this electrostatic force.

The attracting member 123 is additionally equipped with a multiplenumber of heaters HN. These heaters HN are respectively provided in themultiple regions RN of the electrostatic chuck. In the exemplaryembodiment, the multiple heaters HN include a first heater 156, a secondheater 157 and a third heater 158. The first heater 156 is provided inthe first region R1; the second heater 157, in the second region R2; andthe third heater 158, in the third region R3.

The individual heaters HN are connected to a heater power supply 161. Inthe present exemplary embodiment, a filter 163 a is provided between thefirst heater 156 and the heater power supply 161 to suppress the highfrequency power from being introduced into the heater power supply 161.A filter 163 b is provided between the second heater 157 and the heaterpower supply 161 to suppress the high frequency power from beingintroduced into the heater power supply 161. Further, a filter 163 c isprovided between the third heater 158 and the heater power supply 161 tosuppress the high frequency power from being introduced into the heaterpower supply 161.

Multiple first elastic members EM1 are provided between the base 121 andthe cooling table 117. The first elastic members EM1 are configured toallow the electrostatic chuck 120 to be upwardly spaced from the coolingtable 117. Each of the first elastic members EM1 is an O-ring. Theindividual first elastic members EM1 have different diameters and arearranged concentrically with respect to the axis line Z. Further, thefirst elastic members EM1 are located under boundaries between theadjacent regions of the electrostatic chuck 120 and under the edge ofthe electrostatic chuck 120. In the present exemplary embodiment, thefirst elastic members EM1 include an elastic member 165, an elasticmember 167 and an elastic member 169. The elastic member 165 is providedunder a boundary between the first region R1 and the second region R2;the elastic member 167, under a boundary between the second region R2and the third region R3; and the elastic member 169, under the edge ofthe electrostatic chuck 120.

The individual first elastic member EM1 are partially placed in groovesprovided on the first top surface 117 c of the cooling table 117 and incontact with the first top surface 117 c and the bottom surface 121 d ofthe base 121. These first elastic members EM1 define, along with thecooling table 117 and the base 121, a plurality of heat transfer spacesDSN between the first top surface 117 c of the cooling table 117 and thebottom surface 121 d of the base 121. These heat transfer spaces DSN arerespectively extended under the regions RN of the electrostatic chuck120 and separated from each other. In the exemplary embodiment, the heattransfer spaces DSN include a first heat transfer space DS1, a secondheat transfer space DS2 and a third heat transfer space DS3. The firstheat transfer space DS1 is located inside the elastic member 165; thesecond heat transfer space DS2, between the elastic member 165 and theelastic member 167; and the third heat transfer space DS3, between theelastic member 167 and the elastic member 169. As will be describedlater, a gas source GS of a heat transfer gas (for example, a He gas), achiller unit TU and a gas exhaust device VU are connected to the heattransfer spaces DSN selectively via a pipeline system PS. Further, alength of each heat transfer space DSN in a vertical direction is set tobe in a range from, but not limited to, 0.1 mm to 2.0 mm.

In the present exemplary embodiment, each of the first elastic membersEM1 has heat resistivity higher than heat resistivity of each of theheat transfer spaces DSN in which the He gas is supplied. The heatresistivity of each heat transfer space DSN depends on a heatconductivity of the heat transfer gas, a length of the correspondingheat transfer space DSN in the vertical direction and an area thereof.Further, the heat resistivity of each first elastic member EM1 dependson a heat conductivity of the corresponding first elastic member EM1, athickness of the corresponding first elastic member EM1 in the verticaldirection and an area thereof. Thus, a material, the thickness and thearea of each of the first elastic members EM1 are determined based onthe heat resistivity of the corresponding heat transfer space DSN.Furthermore, the first elastic members EM1 may be required to have lowheat conductivity and high heat resistance. Thus, the first elasticmembers EM1 may be formed of, by way of non-limiting example,perfluoroelastomer.

The mounting table 116 may be further equipped with a fastening member171. The fastening member 171 is made of a metal and is configured toclamp the base 121 and the first elastic members EM1 between thefastening member 171 and the cooling table 117. The fastening member 171is made of a material having low heat conductivity, for example,titanium to suppress heat conduction between the base 121 and thecooling table 117 through the fastening member 171.

In the present exemplary embodiment, the fastening member 171 has acylindrical portion 171 a and an annular portion 171 b. The cylindricalportion 171 a has a substantially cylindrical shape, and has a firstbottom surface 171 c at a bottom end thereof. The first bottom surface171 c is a band-shaped surface extended in the circumferential directionthereof.

The annular portion 171 b has a substantially annular plate shape and isextended from the cylindrical portion 171 a inwardly in the diametricdirection to be continuous with an upper inner periphery of thecylindrical portion 171 a. This annular portion 171 b provides a secondbottom surface 171 d. The second bottom surface 171 d is a band-shapedsurface extended in the circumferential direction thereof.

The fastening member 171 is placed such that the first bottom surface171 c is in contact with the second top surface 117 e of the coolingtable 117 and the second bottom surface 171 d is in contact with thesecond top surface 121 e of the base 121. Further, the fastening member171 is fixed to the peripheral portion 117 b of the cooling table 117 bya screw 173. By adjusting screwing of this screw 173 into the fasteningmember 171, a pressed amount of the first elastic members EM1 isadjusted, so that the length of the heat transfer spaces DSN in thevertical direction is adjusted.

In the exemplary embodiment, a second elastic member 175 is providedbetween a bottom surface of an inner peripheral portion of the annularportion 171 b of the fastening member 171 and the second top surface 121e of the base 121. The second elastic member 175 is implemented by anO-ring and is configured to suppress a particle (e.g., metal powder)that might be generated by a friction between the second bottom surface171 d of the fastening member 171 and the second top surface 121 e ofthe base 121 from being moved toward a side of the attracting member123.

Furthermore, the second elastic member 175 generates a reaction forcesmaller than a reaction force generated by the first elastic membersEM1. That is, the first elastic members EM1 are configured such that thereaction force generated by the first elastic members EM1 is larger thanthe reaction force generated by the second elastic member 175. Inaddition, this second elastic member 175 may be made of a materialhaving high heat resistance and low heat conductivity, for example,perfluoroelastomer.

A heater 176 is provided on the fastening member 171. This heater 176 isextended in the circumferential direction and connected to a heaterpower supply 161 via a filter 178. The filter 178 is provided tosuppress the high frequency power from being introduced into the heaterpower supply 161.

The heater 176 is provided between a first film 180 and a second film182. The first film 180 is located closer to the fastening member 171than the second film 182 is. The first film 180 has heat conductivitylower than that of the second film 182. By way of example, the firstfilm 180 may be a thermally sprayed zirconia-based film, and the secondfilm 182 may be a thermally sprayed yttrium oxide (yttria)-based film.Further, the heater 176 may be a thermally sprayed tungsten film.

A focus ring FR is provided on the second film 182. The focus ring FR isheated by heat from the heater 176. Further, most of heat flux from theheater 176 flows toward the second film 182 than the first film 180, andflow toward the focus ring FR through the second film 182. Accordingly,the focus ring FR is efficiently heated.

Furthermore, outer side surfaces of the fastening member 171 and thecooling table 117 of the mounting table 116 and so forth are coveredwith one or more insulating members 186. The one or more insulatingmembers 186 may be made of, by way of example, but not limitation,aluminium oxide or quartz.

In addition, as illustrated in FIG. 11 a gas line 190 through which theheat transfer gas (e.g., He gas) is supplied into a gap between theprocessing target object W and the attracting member 123 is provided inthe cooling table 117 and the electrostatic chuck 120 of the mountingtable 116. The gas line 190 is connected to a heat transfer gas supplyunit 191.

As depicted in FIG. 11, the gas line 190 includes a gas line 190 a, agas line 190 b and a gas line 190 c. The gas line 190 a is formed in theattracting member 123. Further, the gas line 190 c is formed in thecooling table 117. The gas line 190 a and the gas line 190 c areconnected to each other with the gas line 190 b therebetween. The gasline 190 b is implemented by a sleeve 192. This sleeve 192 is asubstantially cylindrical member, and at least a surface thereof hasinsulation property. This surface of the sleeve 192 is made of ceramic.As an example, the sleeve 192 is made of insulating ceramic. By way ofexample, the sleeve 192 is made of aluminium oxide (alumina). As anotherexample, the sleeve 192 may be implemented by a metal member havingthereon a surface on which insulation treatment is performed. Forexample, the sleeve 192 may have a main body made of aluminium and analumite film formed on a surface of the main body.

In the base 121 and the cooling table 117, an accommodation space foraccommodating the sleeve 192 is formed. A film 194 made of insulatingceramic is formed on a surface 121 f of the base 121 which partitionsand forms this accommodation space. The film 194 may be, by way ofexample, but not limitation, a thermally sprayed aluminium oxide(alumina) film.

A third elastic member 196 is provided between the film 194 and thecooling table 117 to hermetically seal the accommodation space of thesleeve 192. The third elastic member 196 is implemented by an O-ring andhas insulation property. The third elastic member 196 may be made of, byway of non-limiting example, perfluoroelastomer. Further, a fourthelastic member 198 is provided at an outside of the third elastic member196. The fourth elastic member 198 is an O-ring and in contact with thefirst top surface 117 c of the cooling table 117 and the bottom surface121 d of the base 121 while sealing the heat transfer space (forexample, the first heat transfer space DS1). The fourth elastic member198 may be made of, by way of example, but not limitation,perfluoroelastomer.

As stated above, in the mounting table 116, the cooling table 117 andthe base 121 are spaced apart from each other by the first elasticmembers EM1. Further, in this mounting table 116, no adhesive is used tocouple the base 121 and the attracting member 123. Accordingly, thetemperature of the electrostatic chuck 120 can be set to be high.Further, since heat transfer between the electrostatic chuck 120 and thecooling table 117 is achieved through the heat transfer gas suppliedinto the heat transfer spaces DSN, it is also possible to set thetemperature of the electrostatic chuck 120 to be low. Furthermore, inthis mounting table 116, a power feed route for the high frequency powerto the base 121 of the electrostatic chuck 120 is secured by the powerfeed body 119, the cooling table 117 and the fastening member 171.Moreover, since the power feed body 119 is not directly connected to thebase 121 of the electrostatic chuck 120 but connected to the coolingtable 117, aluminium or an aluminium alloy can be used as a material forthe power feed body 119. Accordingly, even in case of supplying the highfrequency power of the high frequency equal to or higher than 13.56 MHz,a loss of the high frequency power in the power feed body 119 issuppressed.

In addition, as described above, in the exemplary embodiment, the secondelastic member 175 is provided between the bottom surface of the innerperipheral portion of the annular portion 171 b of the fastening member171 and the second top surface 121 e of the base 121. Since the secondtop surface 121 e of the peripheral portion 121 b of the base 121 andthe second bottom surface 171 d of the fastening member 171 are incontact with each other, friction is generated at the contact pointtherebetween, so that the particle (e.g., metal powder) may be generatedthereat. Even when this particle is generated, the second elastic member175 suppresses the particle from adhering to the attracting member 123and the processing target object W placed on the correspondingattracting member 123.

Further, the first elastic members EM1 are configured such that thereaction force generated by these first elastic members EM1 is largerthan the reaction force generated by the second elastic member 175.Accordingly, the electrostatic chuck 120 can be securely spaced from thecooling table 117.

Furthermore, in the exemplary embodiment, each of the first elasticmembers EM1 is configured to have the heat resistance higher than theheat resistance of the corresponding heat transfer space DSN when the Hegas is supplied in the corresponding heat transfer space DSN. Further,these first elastic members EM1 are made of, by way of example,perfluoroelastomer. With these first elastic members EM1, the heatconduction through the heat transfer spaces DSN is more dominant thanheat conduction through the first elastic members EM1 between theelectrostatic chuck 120 and the cooling table 117. Thus, the temperaturedistribution of the electrostatic chuck 120 can be uniformed.

Additionally, in the exemplary embodiment, the gas line 190 for the heattransfer gas supplied into the gap between the processing target objectW and the attracting member 123 is formed without using any adhesive.Further, the surface 121 f of the base 121, which forms theaccommodation space in which the sleeve 192 as a part of the gas line190 is placed, is covered with the film 194, and the third elasticmember 196 having the insulation property is provided between the film194 and the cooling table 117 to seal the corresponding accommodationspace. With this configuration the introduction of the plasma into thegap between the base 121 and the cooling table 117 and a resultantdielectric breakdown of the base 121 can be supressed.

Furthermore, according to the plasma processing apparatus 100 having theabove-described mounting table 116, a plasma processing can be performedon the processing target object W in a wide temperature range from a lowtemperature to a high temperature.

Now, a pipeline system PS that can be adopted in the plasma processingapparatus 100 will be explained. FIG. 12 is a diagram illustrating apipeline system according to the exemplary embodiment. The pipelinesystem PS shown in FIG. 12 has a multiple number of valves. The pipelinesystem PS is configured to connect the gas source GS, the chiller unitTU and the gas exhaust device VU selectively to each of the heattransfer spaces DSN and to switch a connection and a disconnectionbetween the chiller unit TU and the path 117 f. Below, the descriptionwill be provided for the example where the heat transfer spaces DSNinclude three heat transfer spaces (the first heat transfer space DS1,the second heat transfer space DS2, and the third heat transfer spaceDS3). Here, however, it should be noted that the number of the heattransfer spaces DSN may not be particularly limited, and may be one ormore as long as the number of the heat transfer spaces DSN correspondsto the number of the regions RN of the electrostatic chuck 120.

The pipeline system PS includes a line L21, a line L22, a valve V21 anda valve V22. One end of the line L21 is connected to the chiller unitTU, and the other end of the line L21 is connected to the path 117 f.The valve V21 is provided at a part of the line L21. One end of the lineL22 is connected to the chiller unit TU, and the other end of the lineL22 is connected to the path 117 f. The valve V22 is provided at a partof the line L22. If the valve V21 and the valve V22 are opened, thecoolant is supplied from the chiller unit TU into the path 117 f throughthe line L21. The coolant supplied into the path 117 f is returned backinto the chiller unit TU through the line L22.

Further, the pipeline system PS further includes a pressure controller104 a, a line L11 a, a line L12 a, a line L13 a, a line L14 a, a lineL15 a, a line L17 a, a line L31 a, a line L32 a, a valve V11 a, a lineV12 a, a valve V13 a, a vale V14 a, a valve V15 a, a valve V31 a and avalve V32 a.

The pressure controller 104 a is connected to the gas source GS. One endof the line L11 a is connected to the pressure controller 104 a. Thevalve V11 a is provided at a part of the line L11 a. One end of the lineL15 a is connected to the first heat transfer space DS1, and the otherend of the line L15 a is connected to the gas exhaust device VU. Thevalve V15 a is provided at a part of the line L15 a.

One end of the line L12 a is connected to the other end of the line L11a. The other end of the line L12 a is connected to a part of the lineL15 a on the side of the first heat transfer space DS1 with respect tothe valve V15 a. The valve V12 a is provided at a part of the line L12a. One end of the line L13 a and one end of the line L14 a are alsoconnected to the other end of the line L11 a. The valve V13 a isprovided at a part of the line L13 a, and the valve V14 a is provided ata part of the line L14 a. The other end of the line L13 a and the otherend of the line L14 a are connected to each other. One end of the lineL17 a is connected to a connection point between the other end of theline L13 a and the other end of the line L14 a. The other end of theline L17 a is connected to the line L15 a at a position closer to thevalve V15 a than the other end of the line L12 a is close to the valveV15 a.

One end of the line L31 a is connected to a part of the line L21 on theside of the chiller unit TU with respect to the valve V21. The other endof the line L31 a is connected to the first heat transfer space DS1. Thevalve V31 a is provided at a part of the line L31 a. One end of the lineL32 a is connected to a part of the line L22 on the side of the chillerunit TU with respect to the valve V22. The other end of the line L32 ais connected to the first heat transfer space DS1. The valve V32 a isprovided at a part of the line L32 a.

Further, the pipeline system PS additionally includes a pressurecontroller 104 b, a line L11 b, a line L12 b, a line L13 b, a line L14b, a line L15 b, a line L17 b, a line L31 b, a line L32 b, a valve V11b, a valve V12 b, a valve V13 b, a valve V14 b, a valve V15 b, a valveV31 b and a valve V32 b.

The pressure controller 104 b is connected to the gas source GS. One endof the line L11 b is connected to the pressure controller 104 b. Thevalve V11 b is provided at a part of the line L11 b. One end of the lineL15 b is connected to the second heat transfer space DS2, and the otherend of the line L15 b is connected to the gas exhaust device VU.Further, the valve V15 b is provided at a part of the line L15 b.

One end of the line L12 b is connected to the other end of the line L11b. The other end of the line L12 b is connected to a part of the lineL15 b on the side of the second heat transfer space DS2 with respect tothe valve V15 b. The valve V12 b is provided at a part of the line L12b. One end of the line L13 b and one end of the line L14 b are alsoconnected to the other end of the line L11 b. The valve V13 b isprovided at a part of the line L13 b, and the valve V14 b is provided ata part of the line L14 b. The other end of the line L13 b and the otherend of the line L14 b are connected to each other. One end of the lineL17 b is connected to a connection point between the other end of theline L13 b and the other end of the line L14 b. The other end of theline L17 b is connected to the line L15 b at a position closer to thevalve V15 b than the other end of the line L12 b is close to the valveV15 b.

One end of the line L31 b is connected to a part of the line L21 on theside of the chiller unit TU with respect to the valve V21. The other endof the line L31 b is connected to the second heat transfer space DS2.The valve V31 b is provided at a part of the line L31 b. One end of theline L32 b is connected to a part of the line L22 on the side of thechiller unit TU with respect to the valve V22. The other end of the lineL32 b is connected to the second heat transfer space DS2. The valve V32b is provided at a part of the line L32 b.

Further, the pipeline system PS further includes a pressure controller104 c, a line L11 c, a line L12 c, a line L13 c, a line L14 c, a lineL15 c, a line L17 c, a line L31 c, a line L32 c, a valve V11 c, a valveV12 c, a valve V13 c, a valve V14 c, a valve V15 c, a valve V31 c and avalve V32 c.

The pressure controller 104 c is connected to the gas source GS. One endof the line L11 c is connected to the pressure controller 104 c. Thevalve V11 c is provided at a part of the line L11 c. One end of the lineL15 c is connected to the third heat transfer space DS3, and the otherend of the line L15 c is connected to the gas exhaust device VU.Further, the valve V15 c is provided at a part of the line L15 c.

One end of the line L12 c is connected to the other end of the line L11c. The other end of the line L12 c is connected to a part of the lineL15 c on the side of the third heat transfer space DS3 with respect tothe valve V15 c. The valve V12 c is provided at a part of the line L12c. One end of the line L13 c and one end of the line L14 c are alsoconnected to the other end of the line L11 c. The valve V13 c isprovided at a part of the line L13 c, and the valve V14 c is provided ata part of the line L14 c. The other end of the line L13 c and the otherend of the line L14 c are connected to each other. One end of the lineL17 c is connected to a connection point between the other end of theline L13 c and the other end of the line L14 c. The other end of theline L17 c is connected to the line L15 c at a position closer to thevalve V15 c than the other end of the line L12 c is close to the valveV15 c.

One end of the line L31 c is connected to a part of the line L21 on theside of the chiller unit TU with respect to the valve V21. The other endof the line L31 c is connected to the third heat transfer space DS3. Thevalve V31 c is provided at a part of the line L31 c. One end of the lineL32 c is connected to a part of the line L22 on the side of the chillerunit TU with respect to the valve V22. The other end of the line L32 cis connected to the third heat transfer space DS3. The valve V32 c isprovided at a part of the line L32 c.

Now, the method MT will be discussed for an example case where themethod MT is applied to the processing target object W1 shown in FIG. 2by using the plasma processing apparatus 100. Even in case of using thisplasma processing apparatus 100, the method MT may also be applied toanother type of processing target object such as the processing targetobject W2 shown in FIG. 8. When the method MT is applied to theprocessing target object W2 by using the plasma processing apparatus100, the processes ST7 to ST11 are first performed prior to theprocesses ST1 to ST6.

When the plasma processing apparatus 100 is used, the processing targetobject W1 is prepared within the chamber 112 c in the process ST1 of themethod MT. The processing target object W1 is placed on and held by theelectrostatic chuck 120.

In the subsequent process ST2, the temperature of the processing targetobject W1 is lowered. In the process ST2, the individual components ofthe plasma processing apparatus 100 are controlled in response tosignals from the control unit MCU. FIG. 13 is a diagram illustrating astate of the pipeline system of the plasma processing apparatus shown inFIG. 9 in an example of the process ST2. In this example process ST2, asshown in FIG. 13, the heater power supply 161 is controlled to stop thepower supply to the multiple number of heaters HN. Further, thetemperature of the coolant supplied from the chiller unit TU isadjusted. The valves of the pipeline system PS are controlled such thatthe coolant is circulated between the path 117 f and the chiller unitTU, and the chiller unit TU is connected to the heat transfer spacesDSN. To elaborate, the valve V21, the valve V22, the valve V31 a, thevalve V32 a, the valve V31 b, the valve V32 b, the valve V31 c and thevalve V32 c are opened, while the other valves of the pipeline system PSare closed. In the state of the pipeline system PS shown in FIG. 13, themultiple number of heaters HN do not generate heat, and the coolant issupplied into the heat transfer spaces DSN and into the path 117 f aswell. In the state of the pipeline system PS depicted in FIG. 13, theheat resistance of the heat transfer spaces DSN is reduced, so that thetemperature of the attracting member 123 of the electrostatic chuck 120is reduced at a high speed. Accordingly, prior to etching the siliconoxide in the process ST3, the temperature of the processing targetobject W1 can be reduced at a high speed.

In the subsequent process ST3, the silicon oxide of the processingtarget object W1 is etched in the state that the temperature of theprocessing target object W1 is set to the first temperature. In theprocess ST3, the individual components of the plasma processingapparatus 100 are controlled in response to the signals from the controlunit MCU. Accordingly, the processing gas containing carbon, hydrogenand fluorine is supplied into the chamber 112 c. Further, in the processST3, the chamber 112 c is decompressed. Further, opening/closing statesof the valves of the pipeline system PS and the temperature of thecoolant supplied from the chiller unit TU are controlled such that theprocessing target object W1 is maintained at the first temperature.Further, the first high frequency power is supplied to the base 121 asthe lower electrode from the first high frequency power supply 62.Further, the second high frequency power may be supplied to the base 121from the second high frequency power supply 64. As a result ofperforming the process ST3, the plasma of the processing gas isgenerated within the chamber 112 c. The silicon oxide is etched by theactive species such as ions and/or radicals in this plasma.

Even in case of using the plasma processing apparatus 100, thesubsequent processes ST4, ST5 and ST6 are performed in the same way asin case of using the plasma processing apparatus 10. That is, in theprocess ST4, the light emission intensity of CO is detected by theanalyser 72. In the process ST5, based on the detected light emissionintensity of CO, for example, it is determined by the control unit MCUwhether the etching of the silicon oxide is ended. In the process ST6,it is determined by the control unit MCU whether the etching of a presetnumber of layers of the processing target object W1 is completed.

In the subsequent process ST7, the temperature of the processing targetobject W1 is raised. In the process ST7, the individual components ofthe plasma processing apparatus 100 are controlled in response to thesignals from the control unit MCU. FIG. 14 is a diagram illustrating astate of the pipeline system of the plasma processing apparatus shown inFIG. 9 in an example of the process ST7. In this example process ST7, asshown in FIG. 14, the heater power supply 161 is controlled to supplythe power to the multiple number of heaters HN. Further, the valves ofthe pipeline system PS are controlled such that the coolant iscirculated between the path 117 f and the chiller unit TU, and the gasexhaust device VU is connected to the heat transfer spaces DSN. Toelaborate, the valve V15 a, the valve V15 b, the valve V15 c, the valveV21 and the valve V22 are opened, while the other valves of the pipelinesystem PS are closed. In the state of the pipeline system shown in FIG.14, the heaters HN generate the heat, and the heat transfer spaces DSNare decompressed. In the state of the pipeline system depicted in FIG.14, the heat resistance of the heat transfer spaces DSN is increased, sothat the temperature of the attracting member 123 of the electrostaticchuck 120 is increased at a high speed. Accordingly, prior to etchingthe silicon nitride in the process ST8, the temperature of theprocessing target object W1 can be increased at a high speed.

In the subsequent process ST8, the silicon nitride of the processingtarget object W1 is etched in the state that the temperature of theprocessing target object W1 is set to the second temperature. In theprocess ST8, the individual components of the plasma processingapparatus 100 are controlled in response to the signals from the controlunit MCU. Accordingly, a processing gas containing carbon, hydrogen andfluorine is supplied into the chamber 112 c. Further, in the processST8, the chamber 112 c is decompressed. Further, the opening/closingstates of the valves of the pipeline system PS, the heater power supply161 and the temperature of the coolant supplied from the chiller unit TUare controlled such that the processing target object W1 is maintainedat the second temperature. Further, the first high frequency power issupplied to the lower electrode 18 from the first high frequency powersupply 62. Further, the second high frequency power may be supplied tothe lower electrode 18 from the second high frequency power supply 64.As a result of performing the process ST8, the plasma of the processinggas is generated within the chamber 112 c. The silicon nitride is etchedby the active species such as ions and/or radicals in this plasma.

Even in case of using the plasma processing apparatus 100, thesubsequent processes ST9, ST10 and ST11 are performed in the same way asin case of using the plasma processing apparatus 10. That is, in theprocess ST9, the light emission intensity of CN is detected by theanalyser 72. In the process ST10, based on the detected light emissionintensity of CN, for example, it is determined by the control unit MCUwhether the etching of the silicon nitride is ended. In the processST11, it is determined by the control unit MCU whether the etching of apreset number of layers of the processing target object W1 is completed

As stated above, according to the plasma processing apparatus 100, thetemperature of the processing target object can be decreased orincreased at a high speed. Thus, it is possible to etch the siliconoxide and the silicon nitride selectively against each other with higherefficiency. Further, the processing time of the method MT can bereduced.

Although the various exemplary embodiments have been described so far,those exemplary embodiments are not limiting and can be modified invarious ways. By way of example, although the above-described plasmaprocessing apparatuses 10 and 100 are configured to be of thecapacitively coupled plasma processing apparatus, the method MT and amodification thereof can also be applied to various other types ofplasma processing apparatuses such as an inductively coupled plasmaprocessing apparatus, a plasma processing apparatus using a surface wavesuch as a microwave for the generation of plasma, and so forth.

From the foregoing, it will be appreciated that the exemplary embodimentof the present disclosure has been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the embodiment disclosed herein is not intended to belimiting. The scope of the inventive concept is defined by the followingclaims and their equivalents rather than by the detailed description ofthe exemplary embodiment. It shall be understood that all modificationsand embodiments conceived from the meaning and scope of the claims andtheir equivalents are included in the scope of the inventive concept.

We claim:
 1. A method of etching silicon oxide and silicon nitrideselectively against each other, the method comprising: preparing aprocessing target object within a chamber provided by a chamber mainbody of a plasma processing apparatus; etching silicon oxide of theprocessing target object by generating plasma of a processing gascontaining carbon, hydrogen and fluorine within the chamber in a statethat a temperature of the processing target object is set to a firsttemperature; and etching silicon nitride of the processing target objectby generating the plasma of the processing gas containing carbon,hydrogen and fluorine within the chamber in a state that the temperatureof the processing target object is set to a second temperature higherthan the first temperature, wherein an etching rate of the silicon oxideis higher than an etching rate of the silicon nitride at the firsttemperature, and the etching rate of the silicon nitride is higher thanthe etching rate of the silicon oxide at the second temperature.
 2. Themethod of claim 1, wherein the processing target object has multiplefirst layers made of the silicon oxide and multiple second layers madeof the silicon nitride, the multiple first layers and the multiplesecond layers are alternately stacked on top of each other, and theetching of the silicon oxide and the etching of the silicon nitride areperformed alternately.
 3. The method of claim 1, wherein the firsttemperature is lower than −30° C., and the second temperature is higherthan −30° C.
 4. The method of claim 1, wherein the plasma processingapparatus further comprises an analyzer configured to performspectroscopic analysis of the plasma within the chamber, the etching ofthe silicon oxide is ended when it is determined, based on a lightemission intensity of CO (Carbon Oxide) obtained by the analyzer, thatthe silicon oxide is completely etched, and the etching of the siliconnitride is ended when it is determined, based on a light emissionintensity of CN (Carbon Nitride) obtained by the analyzer, that thesilicon nitride is completely etched.
 5. The method of claim 1, whereinthe plasma processing apparatus further comprises: a mounting tablewhich is provided within the chamber and includes a cooling table, whichis made of a metal and provided with a path for a coolant formedtherein, and an electrostatic chuck, which is provided on the coolingtable with a heat transfer space therebetween and provided with a heatertherein; a chiller unit configured to supply the coolant into the path;a gas exhaust device; and a pipeline system configured to connect thechiller unit and the gas exhaust device to the heat transfer spaceselectively, wherein the method further comprises: decreasing thetemperature of the processing target object by supplying the coolantinto the path and the heat transfer space from the chiller unit; andincreasing the temperature of the processing target object bydecompressing the heat transfer space with the gas exhaust device andgenerating heat from the heater, wherein the etching of the siliconoxide is performed after the temperature of the processing target objectis set to the first temperature by performing the decreasing of thetemperature of the processing target object, and the etching of thesilicon nitride is performed after the temperature of the processingtarget object is set to the second temperature by performing theincreasing of the temperature of the processing target object.